You don't say how far apart the rooms are or how many connections you want. You can simply by a $15 router and connect it between the DSL Router and the incoming line to your computer. Then run Twisted pair ethernet wire to the other computers Ethernet adapter and off you go.

I've used DSL in my home with a phone line network to 5 computers and I just converted that to Wireless 802g. However, my kids are now complaining about the wireless lagging when they play their networked computer games. I am now considering cabling the entire house with Twisted pair ethernet.

Al